1. Field of the Invention
The present invention relates to triarylphosphine oxide derivatives and, more particularly, to triarylphosphine oxide derivatives containing fluorine substituents that are useful as a monomer in preparation of polymers with improved properties such as chemical resistance, electrical insulating and adhesive properties, and flame retardancy.
2. Description of the Related Art
There are known methods of using bis(3-aminophenyl)phenyl phosphine oxide (DAPPO) or diaminodiphenylsulfone (DDS) as a monomer in preparation of a polymer exhibiting excellent adhesive property and flame retardancy, such as polyimide resin (See. M. F. Martinez-Nuez et al., Polymer Prepint, 35, p. 709 (1994)). However, using DDS which contains no phosphine oxide produces a polymer having a low adhesive strength and high dielectric constant and birefringence, while using DAPPO provides a polymer excellent in adhesiveness but still high in dielectric constant and birefringence.
Since fluorine (F) has very high electronegativity, small Van der Walls"" radius comparable to that of hydrogen and a high bonding energy with other elements, the compound containing fluorine substituents provides low intermolecular force and thus low surface energy and low friction. Moreover, fluorine-containing compounds have excellent chemical resistance, flame resistance, heat resistance, electrical insulating property and weather resistance. Therefore, these are utilized in nuclear power plants, solar batteries, optical communications and semiconductor devices. However, the major obstacle of the fluorine-containing compounds is their poor adhesive property due to the poor sticking nature of fluorine.
Accordingly, the invention aims to provide novel triarylphosphine oxide derivatives containing fluorine substituents with improved properties by introducing fluoine substituents to phosphine oxides that are known to have high adhesive strength and flame retardancy.
It is, therefore, an object of the present invention to provide novel triarylphosphine oxide derivatives containing both fluorine and phosphor substituents that are useful in preparation of polymers with improved properties such as adhesiveness and flame retardancy as well as chemical resistance and electrical insulating property.
To achieve the above object of the invention, there is provided triarylphosphine oxide derivatives containing fluorine substituents as represented by the chemical formula 1: 
wherein R1 and R2 are independently a fluorine-substituted alkyl group; and X is hydrogen, a nitro group or an amine group.
There is further provided a method for preparing the triarylphosphine oxide derivatives containing fluorine substituents and a method for preparing polyimides from the derivatives.